Surprise find in Kepler planet hunt: lots of multi-planet systems

NASA's Kepler spacecraft, which is searching for Earth-mass planets orbiting sun-like stars, is finding hundreds of candidate planets, and many more multi-planet systems than expected.

Two years into a 3-1/2-year mission, NASA’s Kepler spacecraft, hunting for planets orbiting some 165,000 stars in the constellation Cygnus, is uncovering planet candidates by the hundreds.

Many of these inhabit multi-planet systems that are unexpectedly flat – the inclination of the planets’ orbits within each of these systems are essentially the same, a feature that may hold clues about how these systems formed and evolved.

Not only is the team uncovering many more multi-planet systems than it had anticipated. But the systems hold the promise of allowing researchers to gain valuable information that can lead to an initial estimation of each planet's density and hence it's bulk composition – is it rocky, a water world, or something else? And they potentially can estimate these traits more quickly than previously thought.

These multi-planet-system discoveries “are very important to the success of the mission,” said David Latham, a researcher at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and a member of the Kepler team. He spoke at a briefing May 23 at the American Astronomical Society's spring meeting underway in Boston.